Field of the Invention
The invention relates to a method for controlling an automatic transmission in a drive train of a motor vehicle and a controller for the automatic transmission of a motor vehicle. The method is used to control an automatic transmission in a drive train of a motor vehicle whose transmission controller carries out a gear selection and a gear shift. A new gear is determined during the gear selection by reference to a characteristic diagram and a new gear that is expected to be engaged shortly is determined by its transmission controller, an initial phase of the gear shift being carried out when the new gear differs from the currently engaged gear, and a gear shift being completed as soon as the gear shift instruction has been generated.
German Patent DE 199 37 716 C1 discloses a method for controlling an automatic transmission in a drive train of a motor vehicle. The publication does not specify when or by which event the initial phase of the gear shift is triggered.
German Published, Non-Prosecuted Patent Application DE 198 19 463 A1 discloses a method for controlling an automatic transmission in a drive train of a motor vehicle whose transmission controller carries out a gear selection and a gear shift. A new gear is determined during the gear selection by reference to gear shift characteristic curves stored in a characteristic diagram, and a gear shift instruction, by which a gear shift is triggered, is generated as soon as a working point of the drive train exceeds a gear shift characteristic curve. If it is possible to shorten the gear shift time required for a gear shifting operation, on one hand, the gear shift comfort for the driver is increased and, on the other hand, it is possible to improve the sporty characteristics of the motor vehicle.
German Published, Non-Prosecuted Patent Application DE 195 33 305 A1 (D2) discloses an automatic transmission based on the object of enabling the driver to make interactive intervention by which the information regarding the transmission behavior that the driver is currently dissatisfied with is transmitted to the control unit of the transmission. The gear shift tendency or the dynamic behavior of an operating point referred to the gear shift characteristic curves of a characteristic diagram are used to carry out a premature gear shift. The gear shift is not carried out shortly but is, instead, brought forward, at the driver""s request.
German Published, Non-Prosecuted Patent Application DE 196 26 193 A1 (D3) discloses a device for controlling programmed automatic variable transmissions for motor vehicles. The control device is composed of an electronic programmed circuit and a multiplicity of sensors that are connected thereto and that supply the circuit with a multiplicity of signals that influence the selection of the driving positions of the automatic transmission. The signals originate from the chassis and from the engine, and additional signals are generated manually by the driver. Further signals that cannot be influenced by the driver sense the physical conditions of the driver. Examples of such conditions are the transpiration rate, the posture in the seat, and the pulse rate, and they are, therefore, physical functions that can change in a stressful or hazardous situation.
It is accordingly an object of the invention to provide a method for controlling an automatic transmission and controller suitable for such a method that overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices and methods of this general type and that shorten the gear shift time required for a gear shifting operation.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a method for controlling an automatic transmission in a drive train of a motor vehicle having a transmission controller selecting and shifting gears of the transmission, including the steps of determining a new gear during a gear selection by referring to a gear shift characteristic curve stored in a characteristic diagram, generating a gear shift instruction to trigger a gear shift as soon as a working point of the drive train exceeds a corresponding point on the gear shift characteristic curve, determining, with the transmission controller, a new gear expected to be engaged shortly and carrying out an initial phase of the gear shift when the new gear differs from the currently engaged gear and as soon as the working point exceeds a pre-defined distance from the gear shift characteristic curve, and completing a gear shift as soon as the gear shift instruction has been generated.
The transmission controller determines the new gear and carries out the initial phase of the gear shifting operation as soon as the working point drops below a predefined distance from a gear shift characteristic curve stored in the characteristic diagram, and the gear shift instruction to trigger the gear shift is generated as soon as the working point of the drive train exceeds the corresponding gear shift characteristic curve.
The advantages of the invention are, inter alia, the fact that the initial phase of the gear shifting operation remains completely unnoticed by the driver. If a predetermined gear that has been determined by the transmission controller as a gear that is expected to be engaged shortly is then not engaged for whatever reason, the lack of engagement does not adversely affect the gear shift comfort in any way.
In accordance with another mode of the invention, preselection characteristic curves running at the pre-defined distance from the individual gear shift characteristic curves are stored in the characteristic diagram.
In accordance with a further mode of the invention, a distance between the preselection characteristic curves and the gear shift characteristic curves is calculated as a function of a transmission type.
In accordance with an added mode of the invention, a distance between the preselection characteristic curves and the gear shift characteristic curves is calculated as a function of a transmission type during ongoing operation.
In accordance with an additional mode of the invention, a gear shift to a gear determined as being expected to be engaged shortly is prohibited if a dynamic correction of the gear shift instruction has taken place.
In accordance with yet another mode of the invention, the prohibited gear shift is carried out as soon as the dynamic correction of the gear shift instruction is eliminated.
In accordance with yet a further mode of the invention, the suppressed new gear is set as being the new gear to be engaged shortly.
In accordance with yet an added mode of the invention, an expected gear shift instruction is predicted by analyzing, in a manual driving mode, a behavior of a driver of the motor vehicle characteristic of a driving style.
With the objects of the invention in view, there is also provided a method for controlling an automatic transmission in a drive train of a motor vehicle having a transmission controller selecting and shifting gears of the transmission, including the steps of determining a new gear during a gear selection by referring to a gear shift characteristic curve stored in a characteristic diagram, generating a gear shift instruction to trigger a gear shift as soon as a working point of the drive train exceeds a corresponding point on the gear shift characteristic curve, determining, with the transmission controller, a new gear expected to be engaged shortly and carrying out an initial phase of the gear shift as soon as the working point exceeds a pre-defined distance from the gear shift characteristic curve, and completing a gear shift as soon as the gear shift instruction has been generated.
With the objects of the invention in view, in an automatic transmission of a motor vehicle, the transmission having gears, there is also provided a transmission controller for controlling a transmission ratio, including a characteristic diagram memory storing transmission ratios to be set as a function of a torque and a variable functionally associated with a speed of the vehicle, gear shift characteristic curves, and preselection characteristic curves lying at a predetermined distance from said gear shift characteristic curves, and a processor programmed to signal an expected new gear to the transmission and to prepare a gear shifting operation when a working point overshoots said preselection characteristic curves and to trigger a gear shifting operation when the working point of the motor vehicle overshoots the gear shift characteristic curves.
In accordance with a concomitant feature of the invention, there are provided a gear selector circuit for determining a new gear of the transmission, said gear selector circuit connected to said processor, and a transmission control unit connected to said processor and to said gear selector circuit, said transmission control unit receiving a new gear signal, preparing a gear shifting operation, and carrying out a gear shift to the new gear as soon as the new gear determined by said gear selector circuit differs from a currently engaged gear.
Other features that are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method for controlling an automatic transmission and controller suitable for such a method, it is, nevertheless, not intended to be limited to the details shown because various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.